The present invention relates to a shape detecting apparatus for optically detecting three-dimensional products or parts such as soldered areas of a printed circuit board, parts attached to the printed board, and bumps in an LSI bonding process.
An apparatus for optically detecting a three-dimensional shape is disclosed in a copending U.S. patent application Ser. No. 181,768 filed on Aug. 27, 1980, U.S. Pat. No. 4,343,553 which is assigned to the same assignee as the present patent application. The apparatus of the copending application is arranged such that an image of an object to be detected by a light segmenting method in which the object is illuminated by a slit light extending in a direction of the width of the object is formed on a storage type solid state image sensing device and a plane image of the light-segmented part of the object is obtained by combining the scanning of the object by the slit light in its height direction and the scanning of the image formed in the image sensing device in its width direction. The apparatus of the copending application has no problem when the object under examination is relatively small and a detecting field of view is narrow. When a large detecting field of view is required, that is, the object is large in size or a number of objects must simultaneously be detected, however, a detecting speed of the image sensing device is slow and its detecting time is longer in order to obtain a high sensitivity of the image detection, while the sensitivity of the image detection is reduced, in order to carry out the detection in a shorter time.
In the above shape detecting apparatus, the slit projector and detector are secured to each other so as to be kept positionally unchanged relative to each other. A slit light projected from the slit projector is narrowest at a cross point of an optical axis of the slit projector and an optical axis of the image detector, and a focal point of the image detector is coincident with the cross point. With this arrangement, when the object lies at the cross point, a shape of the object can be most clearly obtained.
However, the object does not always lie at the cross point depending on its size or shape, for example, a warp of a printed circuit board of which mounted parts or soldered portions are to be detected. This brings about a problem of an out-of-focus.